Conventional weapon systems, including missiles, bombs and artillery shells, may be equipped with a terminal guidance system. A terminal guidance system may refer to an electronic system which may guide a weapon toward a designated target in the last phase of deployment prior to impact. Weapons which employ a terminal guidance system, such as a global positioning system (GPS) receiver, may be referred as precision guided munitions (PGMs). Advantageously, PGMs increase the percentage of enemy targets being destroyed while reducing collateral damage.
A problem associated with PGMs is the lack of coordinate reception capability during adverse weather conditions. For example, if a PGM is deployed in adverse weather conditions, the on-board GPS receiver may be unable to receive signals from GPS satellites. As a result, the PGM may be unable to determine its current GPS coordinates or determine the correct path to strike a desired target. Conventional antenna systems have been employed with PGMs to increase reception capability, but are limited by a number of factors. One type of conventional antenna system is a top-loaded monopole antenna as shown in FIG. 1. The top-loaded monopole antenna is typically placed on the nose of the weapon. The top-loaded monopole antenna is linearly polarized, creates back-looking radiation and suffers from a null in the forward direction along with pattern ripple in azimuth. Another type of conventional antenna system is a fuselage patch antenna 200 which is placed along a side of a weapon as shown in FIG. 2. A fuselage patch antenna, also known as a microstrip antenna, is typically placed on a ground plane of the weapon. A problem associated with a fuselage patch antenna is carrier phase rollup. When a weapon is deployed, a weapon may be spinning which causes a carrier phase rollup. Mitigation of the carrier phase rollup may require the addition of costly hardware/software implementations. Consequently, an improved antenna system is necessary.